Doctor's horrible combination of a statin and ether's not right (12)
I believe the answer is:
anaesthetist
'doctor's' is the definition.
(anaesthetist is a kind of doctor)
'horrible combination of a statin and ether's not right' is the wordplay.
'horrible combination of' indicates anagramming the letters.
'and' says to put letters next to each other (I've seen this in other clues).
'not' suggests deleting specific letters.
'right' becomes 'r' (common abbreviation).
'statin' put after 'ethers' is 'ethersstatin'.
'ethersstatin' with 'r' removed is 'ethesstatin'.
'a'+'ethesstatin'='aethesstatin'
'aethesstatin' with letters rearranged gives 'ANAESTHETIST'.
(Other definitions for anaesthetist that I've seen before include "One preparing patients for operations" , "Hospital theatre worker" , "Number" .)